Trimethylaluminum

Formula: C₃H₉Al
Molecular weight: 72.0851
IUPAC Standard InChI: InChI=1S/3CH3.Al/h3*1H3;
IUPAC Standard InChIKey: JLTRXTDYQLMHGR-UHFFFAOYSA-N
CAS Registry Number: 75-24-1
Chemical structure:
This structure is also available as a 2d Mol file or as a computed 3d SD file
The 3d structure may be viewed using Java or Javascript.
Other names: (CH3)3Al; Aluminum, trimethyl-; Trimethylalane; Trimethylaluminium; UN 1103
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Gas phase thermochemistry data

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Data compiled by: José A. Martinho Simões

Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_gas	-86.5 ± 4.8	kJ/mol	Review	Martinho Simões	Selected data. The enthalpy of formation relies on -1891.3 ± 1.9 kJ/mol for the enthalpy of formation of Al(OOCMe)3(cr) and on 0.9 ± 0.2 kJ/mol for the enthalpy of solution of MeCOOH(l) in toluene Mortimer and Sellers, 1963. Liquid trimethylaluminum contains a very small molar fraction of monomer at 298 K, ca. 0.007% Smith, 1972, so that the "real" liquid should be described as [Al(Me)3]2.
Δ_fH°_gas	-57.0 ± 9.7	kJ/mol	Review	Martinho Simões	Liquid trimethylaluminum contains a very small molar fraction of monomer at 298 K, ca. 0.007% Smith, 1972, so that the "real" liquid should be described as [Al(Me)3]2.
Δ_fH°_gas	-88.7	kJ/mol	Review	Martinho Simões	The enthalpy of formation was quoted from Smith, 1974 and relies on experimental data in Tröber and Stricker, 1966. Liquid trimethylaluminum contains a very small molar fraction of monomer at 298 K, ca. 0.007% Smith, 1972, so that the "real" liquid should be described as [Al(Me)3]2.

Phase change data

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Data compiled as indicated in comments:
TRC - Thermodynamics Research Center, NIST Boulder Laboratories, Chris Muzny director
MS - José A. Martinho Simões
AC - William E. Acree, Jr., James S. Chickos
DH - Eugene S. Domalski and Elizabeth D. Hearing

Quantity	Value	Units	Method	Reference	Comment
T_triple	288.43	K	N/A	McCullough, Messerly, et al., 1963	Uncertainty assigned by TRC = 0.02 K; TRC
Quantity	Value	Units	Method	Reference	Comment
Δ_vapH°	63.2 ± 1.7	kJ/mol	RSC	McCullough, Messerly, et al., 1963	MS

Enthalpy of vaporization

Δ_vapH (kJ/mol)	Temperature (K)	Reference	Comment
43.0	288. to 293.	Fulem, Ruzicka, et al., 2003	AC
39.8	351.	McCullough, Messerly, et al., 1963, 2	Based on data from 336. to 400. K.; AC

Antoine Equation Parameters

log₁₀(P) = A − (B / (T + C))
P = vapor pressure (bar)
T = temperature (K)

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Temperature (K)	A	B	C	Reference	Comment
336.96 to 400.27	4.67984	1724.231	-31.398	McCullough, Messerly, et al., 1963, 2	Coefficents calculated by NIST from author's data.

Enthalpy of sublimation

Δ_subH (kJ/mol)	Temperature (K)	Reference	Comment
60.1	243. to 285.	Fulem, Ruzicka, et al., 2003	AC

Enthalpy of fusion

Δ_fusH (kJ/mol)	Temperature (K)	Reference	Comment
8.7906	288.43	McCullough, Messerly, et al., 1963, 2	DH
8.79	288.4	Domalski and Hearing, 1996	AC

Entropy of fusion

Δ_fusS (J/mol*K)	Temperature (K)	Reference	Comment
30.48	288.43	McCullough, Messerly, et al., 1963, 2	DH

In addition to the Thermodynamics Research Center (TRC) data available from this site, much more physical and chemical property data is available from the following TRC products:

Gas phase ion energetics data

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Data compiled as indicated in comments:
LLK - Sharon G. Lias, Rhoda D. Levin, and Sherif A. Kafafi
RDSH - Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. Herron

Ionization energy determinations

IE (eV)	Method	Reference	Comment
9.09 ± 0.26	EI	Winters and Kiser, 1967	RDSH
9.76	PE	Barker, Lappert, et al., 1975	Vertical value; LLK

Appearance energy determinations

Ion	AE (eV)	Other Products	Method	Reference	Comment
Al⁺	14.6 ± 0.2	?	EI	Winters and Kiser, 1967	RDSH
CH₃Al⁺	13.9 ± 0.3	?	EI	Winters and Kiser, 1967	RDSH
C₂H₆Al⁺	10.1 ± 0.3	CH₃	EI	Winters and Kiser, 1967	RDSH

Ion clustering data

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Data compiled by: John E. Bartmess

Note: Please consider using the reaction search for this species. This page allows searching of all reactions involving this species. Searches may be limited to ion clustering reactions. A general reaction search form is also available.

Clustering reactions

+ Trimethylaluminum = ( • )

By formula: H^- + C₃H₉Al = (H^- • C₃H₉Al)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	>354.8 ± 2.1	kJ/mol	IMRB	den Berg, Ingemann, et al., 1992	gas phase; Hydride affinity > (CF3)2CO. Computations indicate HOF(A-) ca. -46 kcal/mol, dHaff ca. 74 kcal/mol

Vibrational and/or electronic energy levels

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Data compiled by: Marilyn E. Jacox

State: X

Vib. sym.	No.	Approximate type of mode	cm^-1		Med.	Method	References


a₁'	1	CH₃ s-stretch	2920		gas	Ra	O'Brien and Ozin, 1971
	2	CH₃ deform.	1200		gas	Ra	O'Brien and Ozin, 1971
	3	AlC₃ s-stretch	530		gas	Ra	O'Brien and Ozin, 1971
a₂	7	CH₃ a-stretch	2948	s	Ar	IR	Kvisle and Rytter, 1984
	9	CH₃ rock	744	vs	gas	IR	Atiya, Grady, et al., 1991
	9	CH₃ rock	742	s	Ar	IR	Kvisle and Rytter, 1984
e'	11	CH₃ a-stretch	2982	m	gas	IR Ra	O'Brien and Ozin, 1971 Atiya, Grady, et al., 1991
	11	CH₃ a-stretch	2971	s	Ar	IR	Kvisle and Rytter, 1984
	12	CH₃ s-stretch	2901	m	gas	IR Ra	O'Brien and Ozin, 1971 Atiya, Grady, et al., 1991
	12	CH₃ s-stretch	2905	m	Ar	IR	Kvisle and Rytter, 1984
	13	CH₃ a-deform.	1430	w T	gas	IR Ra	O'Brien and Ozin, 1971 Atiya, Grady, et al., 1991
	13	CH₃ a-deform.	1430	w T	Ar	IR	Kvisle and Rytter, 1984
	14	CH₃ s-deform.	1202	s	gas	IR	Atiya, Grady, et al., 1991
	14	CH₃ s-deform.	1196	s	Ar	IR	Kvisle and Rytter, 1984
	15	CH₃ rock	754	s T	gas	IR Ra	O'Brien and Ozin, 1971 Atiya, Grady, et al., 1991
	16	AlC₃ a-stretch	691	m s	gas	IR	Atiya, Grady, et al., 1991
	16	AlC₃ a-stretch	689	s	Ar	IR	Kvisle and Rytter, 1984
	17	AlC₃ deform.	170		gas	Ra	O'Brien and Ozin, 1971
e	18	CH₃ a-stretch	2951		gas	Ra	O'Brien and Ozin, 1971
	19	CH₃ a-deform.	1440		gas	Ra	O'Brien and Ozin, 1971
	20	CH₃ rock	717	w	Ar	IR	Kvisle and Rytter, 1984

Additional references: Jacox, 1994, page 400

Notes

Weak

Medium

Strong

Very strong

Tentative assignment or approximate value

References

Go To: Top, Gas phase thermochemistry data, Phase change data, Gas phase ion energetics data, Ion clustering data, Vibrational and/or electronic energy levels, Notes

Martinho Simões
Martinho Simões, J.A., Private communication (see http://webbook.nist.gov/chemistry/om/). [all data]

Mortimer and Sellers, 1963
Mortimer, C.T.; Sellers, P., J. Chem. Soc., 1963, 1978.. [all data]

Smith, 1972
Smith, M.B., J. Organometal. Chem., 1972, 46, 31. [all data]

Smith, 1974
Smith, M.B., J. Organometal. Chem., 1974, 76, 171. [all data]

Tröber and Stricker, 1966
Tröber, A.; Stricker, C., Wiss Z. Tech. Hochsch. Chem. "Carl Schlorlemmer" Leuna-Merseburg, 1966, 8, 34. [all data]

McCullough, Messerly, et al., 1963
McCullough, J.P.; Messerly, J.F.; Moore, R.T.; Todd, S.S., J. Phys. Chem., 1963, 67, 677. [all data]

Fulem, Ruzicka, et al., 2003
Fulem, M.; Ruzicka, K.; Ruzicka, V.; Hulicius, E.; Simecek, T.; Melichar, K.; Pangrác, J.; Rushworth, S.A.; Smith, L.M., Vapor pressure of metal organic precursors, Journal of Crystal Growth, 2003, 248, 99-107, https://doi.org/10.1016/S0022-0248(02)01840-7 . [all data]

McCullough, Messerly, et al., 1963, 2
McCullough, J.P.; Messerly, J.F.; Moore, R.T.; Todd, S.S., Trimethylaluminum: thermodynamic functions in the solid and liquid states, 0-380°K, vapor pressure, heat of vaporization, and entropy in the ideal gas state, J. Phys. Chem., 1963, 67, 677-679. [all data]

Domalski and Hearing, 1996
Domalski, Eugene S.; Hearing, Elizabeth D., Heat Capacities and Entropies of Organic Compounds in the Condensed Phase. Volume III, J. Phys. Chem. Ref. Data, 1996, 25, 1, 1, https://doi.org/10.1063/1.555985 . [all data]

Winters and Kiser, 1967
Winters, R.E.; Kiser, R.W., Ionization and fragmentation of dimethylzinc, trimethylaluminum, and trimethylantimony, J. Organometal. Chem., 1967, 10, 7. [all data]

Barker, Lappert, et al., 1975
Barker, G.K.; Lappert, M.F.; Pedley, J.B.; Sharp, G.J.; Westwood, N.P.C., Bonding studies of boron and the group 3-5 elements. Part XV. He(I) photoelectron spectra of monomeric group 3 tri-halide, trimethyl, and mixed halogenomethyl species, J. Chem. Soc. Dalton Trans., 1975, 1765. [all data]

den Berg, Ingemann, et al., 1992
den Berg, K.J. van; Ingemann, S.; Nibbering, N.M.M., Gas Phase Reactions of Negative Ions with Trimethylaluminum: Formation and Reactivity of the Me3AlH- Ion., Org. Mass Spectrom., 1992, 27, 4, 523, https://doi.org/10.1002/oms.1210270427 . [all data]

O'Brien and Ozin, 1971
O'Brien, R.J.; Ozin, G.A., J. Chem. Soc. A, 1971, 1136. [all data]

Kvisle and Rytter, 1984
Kvisle, S.; Rytter, E., Spectrochim. Acta 40A, 1984, 939. [all data]

Atiya, Grady, et al., 1991
Atiya, G.A.; Grady, A.S.; Russell, D.K.; Claxton, T.A., Spectrochim. Acta, 1991, 47A, 467. [all data]

Jacox, 1994
Jacox, M.E., Vibrational and electronic energy levels of polyatomic transient molecules, American Chemical Society, Washington, DC, 1994, 464. [all data]

Notes

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Symbols used in this document:

AE	Appearance energy
T_triple	Triple point temperature
Δ_fH°_gas	Enthalpy of formation of gas at standard conditions
Δ_fusH	Enthalpy of fusion
Δ_fusS	Entropy of fusion
Δ_rH°	Enthalpy of reaction at standard conditions
Δ_subH	Enthalpy of sublimation
Δ_vapH	Enthalpy of vaporization
Δ_vapH°	Enthalpy of vaporization at standard conditions

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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